Tag Archives: volatileorganiccompounds

VOCs in the news #2

Here’s our latest summary of news items where volatile organic compounds (VOCs) have been the focus of attention.

David Barden

Malaria makes mouse odour more appealing to mosquitoes

MosquitoResearchers from Swiss Federal Institute of Technology in Zurich, Switzerland, have shown that the volatile blends released from malaria-infected mice make them more attractive to mosquitoes. Mark Mescher and colleagues found that the attractiveness increased significantly after acute symptoms had subsided but while the mice remained highly infectious. This supports the hypothesis that the malarial parasite is manipulating the mouse’s odour for its own benefit – in this case, by maximising the probability of the mouse being bitten by more mosquitoes, and so spreading the parasite.

In a separate experiment, VOC profiles from healthy and malaria-infected mice were investigated using a chamber to sample volatiles from the live mice onto an absorbent, followed by analysis using GC–MS and GC–FID. The researchers found that overall volatile emissions fell during the early, acute stage of infection, but then periodically increased during the later stages. They found 11 compounds to be important predictors of infection status during the chronic phase of the disease, while only one compound – 2-hexanone – was an important predictor of infection status during both the chronic and postchronic phases.

These findings could lay the foundation of a method to disrupt signalling from infected animals to mosquitoes, as well as indicating diagnostic biomarkers. The authors describe their work as “an important proof of concept regarding the identification of volatile biomarkers of malaria infection”.
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World Health Organisation calls for indoor e-cigarette ban

e-cigarettesE-Cigarettes remain in the media spotlight, with a report from the WHO calling for their use indoors to be prohibited, and for e-cigarette advertising to be restricted. The report found insufficient evidence to support a conclusion that e-cigarettes help users quit smoking, points out that e-cigarette aerosol is not merely “water vapour” as is often claimed, and says that although the devices are less toxic than conventional cigarettes, they may pose threats to susceptible groups.

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The smell of money

1 dollar billA Californian firm, KWJ Engineering, has identified the chemical fingerprint of banknotes. One hundred $1 bills in various states (from fresh to used) were incubated at 23°C and 40°C, and the volatiles collected onto an SPME fibre, with analysis by TD–GC–MS. The profiles were found to vary considerably from note to note, but a common ‘signature’ was eventually found, which included aldehydes, furans and organic acids at “a small fraction of a ppm”. The next challenge, they say, will be to implement this technology in a backpack device that can be used by border guards to detect smuggling.

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Food analysts look to advanced GC techniques for chemical fingerprinting

Sample vials in a trayAn article in Laboratory Talk, including interviews with industry analysts, highlights how chemical fingerprinting using GC×GC–TOF MS could play its part in tackling the issues highlighted by the recent Elliot Review into the integrity and assurance of food supply networks.

In the article, Julian South from food testing firm Campden BRI says “There is a lot of talk that chemical fingerprinting is going to become a routine form of analysis for contract labs in the near future”. This comment is mirrored by Dionisis Theodosis from analytical laboratory Exova, who says “I am quite optimistic about chemical fingerprinting”. However, both scientists caution that the whole concept of chemical fingerprinting is some way from being a routine tool in the hands of food chemists.

VOCs from petroleum industry can cause ozone pollution in winter as well as summer

Oil field in winterLow-level ozone normally occurs where high levels of VOCs are exposed to strong summer sunlight, but this isn’t always the case – and now research led by Steven Brown at NOAA Earth System Research Laboratory, Boulder, USA, has shown how this happens.

In a paper published in the journal Nature, they use computer simulations to model observations made in a remote Utah oilfield over a sequence of three winters. They found that rapid ozone production in winter could result from a combination of high VOC emissions into a shallow, stable boundary layer, and increased photolysis due to reflected light from snow-cover.

The authors say that winter production of ozone could have “as yet unrecognised consequences”, especially in regions that experience stable winter weather, and that their study will help to better define this emerging air quality issue.

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A light at the end of the tunnel – E-cigarette analysis made easy with TD and TOF MS

e-cigaretteSmoking has never been far from the headlines over recent months, with the forthcoming ban on smoking in cars carrying children in England and Wales having gained a considerable amount of media attention, and the rise in awareness in indirect impacts of smoking such as third-hand smoke.

A particular focus of attention has been the e-cigarette phenomenon and the potential for harm from these mimics of real cigarettes. As a consequence, the UK Government has proposed a ban on e-cigarette sales to under-18s in England, and there are also moves afoot in the USA, with e-cigarettes proposed to come under the remit of the US FDA.

E-cigarette liquids vary widely in composition, but typically contain a variety of flavourings, with or without nicotine, dissolved in a carrier liquid such as glycerol or propylene glycol (1,2-propanediol). Heating this liquid within the e-cigarette generates a vapour, which following inhalation into the lungs, generates a visible ‘fume’ upon exhalation.

However, a meta-review of e-cigarette constituents, published earlier this year, found that commerical e-cigarette solutions can contain a number of potentially harmful chemicals, including formaldehyde, nitrosamines, and polycyclic aromatic hydrocarbons (PAHs). The presence of such chemicals naturally gives rise to some concern, and has already led analytical scientists to examine e-cigarette vapour itself in more detail.

One such study was carried out last year by Tobias Schripp and co-workers at the Fraunhofer Wilhelm-Klauditz-Institut (WKI) in Braunschweig, Germany. They used chamber sampling with Markes’ UNITY-ULTRA and GC–quadrupole MS to identify the mix of chemicals that is released upon ‘vaping’, and how this changes after exhalation.

However, a presentation by Stuart Martin and Chris Rawlinson (of tobacco company British American Tobacco – BAT) at a scientific conference on Smoke Science & Product Technology in September 2013 makes a compelling case that quadrupole MS detectors are not sufficiently sensitive to adequately characterise vapour from e-cigarettes. This is because although e-cigarettes emit a lot less particulate matter than regular tobacco, since no combustion takes place, they still produce a wide range of compounds at trace levels.

Having previously been in conversation with our specialists on how to analyse cigarette smoke, Martin and Rawlinson turned to our TD–GC–TOF MS system to tackle the problem of e-cigarettes. They weren’t disappointed. The concentrating power of TD and sensitivity of the BenchTOF not only allowed them to identify about 130 components (twice as many as before), but greatly shortened the sampling too, because they were able to replace the cumbersome smoking machine with a much simpler syringe drive. This collected just 25 mL of e-cigarette vapour on to a TD tube packed with Tenax TA and SulfiCarb, which was then conveniently desorbed on a Markes TD-100 before transfer to the GC–MS.

Remarkably, the total time for analysis and data-processing was less than 30 minutes – a speed that they say could allow 100 samples to be processed every day, a vast improvement on the eight samples per day obtainable with existing technology. At the same time, they were able to reduce limits of detection from 0.1 µg to less than 5 ng on-tube – a 20-fold increase in sensitivity.

Dr David BardenThe presentation concludes that, although existing analytical ‘smoking machines’ in conjunction with GC–quadrupole MS, may be suitable for assessing the bulk components of e-cigarettes, they are not suitable for in-depth screening, and present the combination of Markes’ TD and TOF MS technologies as a powerful alternative.

VOCs in the news

As part of our regular sweep of news items in the analytical sciences, we often come across instances where volatile organic compounds (VOCs) are the focus of attention. We thought it might be useful and interesting to bring these together in a regular round-up – so here’s the first!

VOCs used to profile bacteria

VOCs emitted by cultures of ten strains of the diarrhoea-causing bacterium Clostridium difficile have been profiled using a custom-built headspace–TOF MS setup. Paul Monk and colleagues at the University of Leicester, UK, identified 69 VOCs and used them to distinguish between the strains – methanol, p-cresol, dimethylamine, ethylene sulfide, dimethyl sulfide and methyl thioacetate were most of value. The authors say that their method “may have utility as a rapid means of identifying C. difficile infection”.

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The case for phthalates as endocrine disruptors strengthens

The case for phthalates being endocrine disruptors has been further bolstered by research carried out by John Meeker and Kelly Ferguson at the University of Michigan, Ann Arbor, USA. They used HPLC–MS–MS to assess urinary levels of 13 phthalate metabolites – primarily oxygenated and singly-hydrolysed derivatives of phthalate esters. Significant reductions of testosterone were found in both men and women of different ages. Notably, substantial increases in metabolites of bis(2-ethylhexyl) phthalate (dioctyl phthalate) in 6–12-year-old boys were associated with a 29% drop in testosterone.

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Apple tightens regulations on hazardous solvents

Benzene and n-hexane have been banned from use as cleaning agents and degreasers in the final assembly process at 22 of Apple’s iPhone and iPad production plants. Their new Regulated Substances Specification additionally stipulates that “All cleaning agents and degreasers used at final assembly process facilities for the manufacturing of Apple products shall be tested for benzene, n-hexane and chlorinated organic solvent content at a certified lab prior to use in production”, and that permitted levels in the breathing zone of workers must be <100 mg/m3 (28 ppm) for n-hexane, and <0.32 mg/m3 (0.1 ppm) for benzene.

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US National Academy of Sciences concludes that formaldehyde causes cancer

The long-running debate in the US over whether formaldehyde is carcinogenic took moved forward in August with the publication of a report by the US National Academy of Sciences (NAS), where they conclude that the answer is “yes it is”.

This follows their critical 2011 review of the US EPA’s draft assessment of formaldehyde. Although the EPA document said that the evidence is “sufficient to conclude a causal association” between formaldehyde exposure and a variety of cancers, the NAS review said that there were “recurring methodologic problems” in this study.

The new document from NAS is their own independent assessment of the literature through to November 2013. Here they conclude that there is “sufficient evidence of carcinogenicity” in humans for nasopharyngeal cancer, sinonasal cancer and myeloid leukemia, and “convincing relevant information” that formaldehyde induces mechanistic events associated with the development of cancer.

These and other aspects lead the committee to conclude that “formaldehyde should be listed in the RoC [Report on Carcinogens] as “known to be a human carcinogen”.”.

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Is carbon tetrachloride still being emitted despite global ban?

Studies carried out by a team led by Qing Liang at the NASA Goddard Space Flight Center, Maryland, USA, have suggested that the observed slow decline of the ozone-depleting carbon tetrachloride (tetrachloromethane) can only be explained if it is still being emitted (see also this press release). This stands in contrast to the near-zero emissions estimate based on production and feedstock usage, a result of the regulations initiated by the 1987 Montreal Protocol.
Liang’s research, which is based on computer modelling of the concentration gradient between the northern and southern hemispheres, estimates that current unknown emissions are still about 30% of pre-treaty peak emissions. He says “it is now apparent there are either unidentified industrial leakages, large emissions from contaminated sites, or unknown CCl4 sources”.

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